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Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?)
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Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?)


  • Subject: Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?)
  • From: David A Rowland <email@hidden>
  • Date: Wed, 6 Sep 2006 20:47:36 -0700

At 10:36 PM -0400 9/6/06, Jeff Birac wrote:
On Sep 6, 2006, at 10:13 PM, David A Rowland wrote:

At 9:29 PM -0400 9/6/06, Jeff Birac wrote:
Clarification:  I am employing the Open PowerPlant framework.

I am trying to minimize warnings, but some would lead to me modifying code I am weary of touching (e.g., PowerPlant).

The (PowerPlant) code is riddled with warnings like:
warning: 'class LAttachment' has pointer data members
but does not override 'LAttachment(const LAttachment&)'
or 'operator=(const LAttachment&)'
warning: 'class LAttachable' has pointer data members
but does not override 'operator=(const LAttachable&)'
warning: 'LUndoer::mAction' should be initialized in the member initialization list


Are these warnings really important or are they just there to encourage "good practice"? If these are frivolous warning, then how would I turn them off; I have not found any flag/switch/preference to ignore such warnings.

I am reluctant to override the implicit any PowerPlant class' Copy Constructor or Assignment Operator because their developers may have a reason to allow (or rely on) the implicit implementations.


They are there to enforce good practice, but they are not frivolous. If you use the default copy or assign for an object with pointer members, you will end with two objects having pointers to the same structures. That could be disaster. For example, if one of the copies goes out of existence and calls the destructor, does the destructor free the objects pointed at? If so, the remaining copy will point to invalid space. If not, where is the pointed at thing freed?


The warning is telling you to think about it and perhaps use a "deep" copy that copies not only the top object but also the pointer destinations.

The warning on LUndoer is probably less serious. mAction must have a default constructor, so you may be OK using it by default. In fact, I'm surprised that's even a warning.

David

Thanks for the explanations...

They are there to enforce good practice, but they are not frivolous. If you use the default copy or assign for an object with pointer members, you will end with two objects having pointers to the same structures. That could be disaster. For example, if one of the copies goes out of existence and calls the destructor, does the destructor free the objects pointed at? If so, the remaining copy will point to invalid space. If not, where is the pointed at thing freed?

LArray makes important use of such overrides to copy an array's items into a separate Handle. But these warnings are kind of cluttering up the build results. Is there a way to regulate these (and other) warnings that do not have seemingly explicit build options?



I'm a bit puzzled by the terminology. "override" usually means what a function in a derived class does to a function of the same name in a base class. "overload" means to give several functions in the same class the same name but different signatures (parameters). The warning messages say "override", but I think they mean "overload".


I don't know how to suppress those particular warnings. You could write an explicit overloading assignment operator and copy constructor, but I would rather live with the warning than clutter the code.

You know the "Rule of Three"? At least that is what I call it. The copy constructor, overloaded assignment operator and destructor tend to occur together. That is, if you have one you often need the others.

David
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  • Follow-Ups:
    • Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?)
      • From: Rua Haszard Morris <email@hidden>
References: 
 >Resolving EXC_BAD_INSTRUCTION (Where do I begin?) (From: Jeff Birac <email@hidden>)
 >Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?) (From: "William H. Schultz" <email@hidden>)
 >Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?) (From: Paul Walmsley <email@hidden>)
 >Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?) (From: Jeff Birac <email@hidden>)
 >Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?) (From: David A Rowland <email@hidden>)
 >Re: Resolving EXC_BAD_INSTRUCTION (Where do I begin?) (From: Jeff Birac <email@hidden>)

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